Acoustic wave receiver for underwater seismic prospecting

ABSTRACT

Acoustic wave receiver for underwater seismic prospecting comprising a plurality of tubular sections filled with liquid and containing coupled pressure sensors, at least one impedance adapter, electric wires interconnecting said sensors, a multiconductor cable and towing cables, end couplers at the extremities of section comprising means for anchoring the towing cables and means for electric connection to the multiconductor cable, said sections being coupled by means of coupling sleeves surrounding the end couplers in a tight manner.

United States Patent H 1 1 3,713,085

Laurent et al. 1 Jan. 23, 1973 ACOUSTIC WAVE RECEIVER FOR [56]References Cited UNDERWATER SEISMIC UNITED STATES PATENTS PROSPECTING n1 Laurem, saint Germain en 33324132; 311322333223;?:1333:iiiiiiiiijiiiiiiiiiilfiilS Laye; Claude Duconge, LeVesinet,

both of France Primary Examiner-Benjamin A. Borchelt [73] Assignee:lnstitnt Francais du Petrole, des ssistant xam ne -R. Kinberg Carburantset Lubrifiants, Rueil AttorneyCraig,Antonelli,Stewart&Hill Malmaison,France 22 Filed: Dec. 29, 1970 [57] ABSTRACT pp No: 102,416 Acoustic;wave receiver for underwater seismic prospecting comprising a pluralityof tubular sections filled with liquid and containing coupled pressuresen- [30] Foreign Applicafim priority Dam sors, at least one impedanceadapter, electric wires interconnecting said sensors, a multiconductorcable Dec. 30, I969 France ..6945582 and towing cables, end couplers atthe extremities of section comprising means for anchoring the towing ca-[52] U.S.Cl ..340/7 l n m n r e ri connection to the mul- [5l] lnt.Cl...Glv 1/20 ticonductor cable, said sections being coupled by [58] Fieldof Search ..340/7 means of coupling sleeves surrounding the end couplersin a tight manner.

Claims, 10 Drawing Figures 18 Ll 1. [1 231 36 35 ii 25 2L1 23 L7 38a 38bs 1 A0 2 27322. 510 2827929 1.9 L6 is 242 PATENTED JAN 2 3 7 sum 1 BF 4ACOUSTTC WAVE RECEIVER FOR UNDERWATER SlEllSMlC PROSPECTING Thisinvention relates to underwater seismic prospecting using a receiver forthe acoustic waves generated from a sonic source after reflection on thereflecting strata of the submerged soil.

The invention is more particularly concerned with a receiving devicewherein the pressure sensors are distributed at selected intervals alongan immersed elongated casing filled with liquid and usually called astreamer.

The streamers are formed from an assembly of sections coupled end-to-endand which house hydrophones with traction cables and electric conductorsinterconnecting the hydrophones.

These different sections must be adapted for a simple and quickconnection to one another and be easily replaceable. Moreover theconnection between the electric conductors of two adjacent sections mustbe effected in an electrically insulated zone.

Amongst the most common embodiments of streamer sections there will bementioned those wherein each group of pressure sensors is positioned bymeans of collars surrounding the casing or by fastening to the towingcables. The fastenings may be achieved for example by providing in asensor-supporting member passageways for the cables on which sleeves aresubsequently set on both sides of the supporting member. Another mode offastening consists in gripping the cables between deformable elementssecured to a sensor supporting member. The assembling and disassemblingrequires tools for clamping or removing the fastening members insertedon the support member of the sensors.

The method for connecting two adjacent sections consists in most casesin introducing the end part of each section in a coupling sleeve. Thefastening is insured by external collars. Towing cables and electricconductors connecting the sensors of two adjacent sections areinterconnected inside the sleeve which is filled with oil. The maindisadvantage of this type of coupling is in the fact that the connectorsof the electric conductors are not insulated against short circuitswhich might result from an accidental intrusion of water at any place ofa section and are in contact with the oil. Moreover the towing cablesand the electric conductor cannot be easily disassembled. in some casesthe disassembling can not be made without a partial destruction of theconstituting elements of the assembly.

It is therefore an object of this invention to provide a new seismicstreamer wherein a. the elements are prefabricated, interchangeable andpermutable and they are easy to assemble and disassemble,

b. the coupling members of any pair of adjacent sections are providedwith a strictly tight housing wherein are connected the electricalconductors,

c. the towing cables contained in each section are connected in asimplified manner to each coupling member joining two adjacent sections.

in the device of the invention each section comprises a multi-conductorelectric cable provided with a sleeve near each of its end parts, saidsleeve having a head.

Moreover each section terminates at each end thereof with an end couplerhaving two recesses or cavities separated by a bearing formed by aninner protrusion of the wall thereof, and on which the head of thesleeve of the multi-conductor cable comes to rest.

The towing cables of each section are associated with anchoring meanssecured within the end coupler at the region of a first cavity. Theselected anchoring means make possible a rapid and particularly simpleassembling operation.

For the connection of the multi-conductor cables with one another, theconductors of each cable are joined to a connector fastened at apredetermined angular position to the end of the coupler portioncontaining the second cavity.

The device further comprises a coupling sleeve having an internalsection substantially equal to the external section of the couplerportion containing the second cavity. Each coupler is introduced in thesleeve with a predetermined angular position and secured in suchposition.

This assembling manner insures a particularly simple and accurateguiding and fitting of the connectors.

The end part of the sleeve of the multi-conductor cable comprises meansfor fastening the head thereof to the bearing of the coupler said meansbeing detachable without deterioration of the different parts.

Finally the joining of the connectors is carried out in an electricallyinsulated zone by making the second cavity tight to the liquid containedin the section and to the medium external to the receiver throughsealing means associated to the head of the multi-conductor cable andplaced on the external surface of the coupler end contained in saidcoupling sleeve.

The advantages of the present invention will be more fully understoodfrom the following description illustrated by the accompanying drawingswherein FIGS. 1 A and l B show the two traction cables contained in eachsection of the seismic streamer;

FIG. 2 shows the multi-conductor cable provided at each end withfastening and sealing means;

FIG. 3 shows more in detail each fastening and sealing means of thecable of FIG. 2;

FIG. 4 is a diagrammatic view of the arrangement of each group ofpressure sensors inside each section;

FIG. 5 is a side view showing the arrangement of each group of pressuresensors inside each section;

FIG. 6 is a perspective view of the coupling members fastened to eachend of the seismic streamer sections;

FIG. 7 is a cross-sectional view along line AA and partially along BB ofthe assembly of the coupling members illustrated in FIG. 6;

FIG. 8 is a front view of the metal pieces for the anchoring of thetowing cables; and

FIG. 9 illustrates another embodiment of anchoring and fastening of thetowing cables.

Referring now more specifically to FIGS. 1 A and l B illustrating twotowing cables 1 and 3, respectively, there is shown the cable 1, at bothends, cylindrical steel sleeves 2 a and 2 b which may, for example beset on the cable by stamping.

The cable 3 is also provided at both ends with sleeves 4 a and 4 b, butalso with further intermediate sleeves at regular intervalscorresponding to the selected spacing between the pressure sensors, saidintermediate sleeves being fastened to the cable, for instance bysetting.

The multi-conductor cable 6 shown in FIGS. 2 and 3 insures thetransmission of the electric signals issued from the sensors distributedalong the streamer. The cable is formed of conductors contained in asheath 7 of constant thickness, made, for example of plastic material.

On each end of this cable 6, of a length slightly greater than that ofthe section, is fitted a metal sleeve 8 having a head 9 provided with acircular groove 10 wherein a toric joint can be received or housed. Thehead 9 is extended with a threaded portion 11. A ring 12 is imbeddedinto the sheath 7 and the sleeve is drawn on the sheath. The fasteningmeans also insures the sealing of the conductors from the oil containedin the sheath. A certain sheath length is cut off at each end so as tohave the ends of the conductors extending there from.

In FIGS. 4 and 5 the pressure sensors 14 a and 14 b are grouped by pairsand associated with sleeves 5 distributed over the length of cable 3.The pressure sensors may be, for example, of the type described in thedescribed in the US. Pat. application Ser. No. 727,953 filed on May 9,1968, and are connected to a strand of three conductors 16a, 16b, and 16c which may be subjected to series or parallel grouping combinations.

Sensors 14 a and 14 b are associated with an intermediate element 15, egof plastic material, having a diameter substantially equal to the innerdiameter of the sheath 18 covering each streamer section.

Grooves 17 a, 17 b, and 17 (FIG. are provided in element 15 in adirection parallel to the axis of the streamer section, forming apassage way for the conductors 16a, 16 b, and 16 c. The output terminals141a and 141 b (FIG. 4) of the two sensors are interconnected with a rod19 a, passing through the groove 17 a. The conductor 16 a iselectrically connected about at mid-way 191 of said rod. Similarly thetwo opposite output terminals of the two sensors are connected through arod 19 b having substantially at mid-way thereof the conductor 16 belectrically connected.

Grooves 20 a and 20 b (FIG. 5) are provided over the whole length ofelement 15 and on the periphery thereof for the passage of cables 1 and3. Moreover a housing opening or recess 21 for receiving the sleeve 5,fastened to cable 3, is provided in element 15. The sleeve 5 isintroduced therein, thereby anchoring the group of sensors in a steadylocation.

Another housing opening 22, provided along the whole length of element15, forms a passageway for the multiconductor cable 6.

Each section also comprises a transformer and a preamplifier forimpedance matching, which are not shown in the figures. These elementsand more generally all the measuring instruments housed in the sheath,are secured to support members similar to element 15 and provided withgrooves such as 17, 20 and 22 and housing openings as 21.

These grooves and housing openings make possible a quick assembling anddisassembling of the cables and the conductors which are maintainedseparate from one another and cannot therefore be wound up or commingledduring the streamer reeling or unreeling operations.

As shown in FIGS. 6 and 7, the end of the streamer section contained inthe sheath 18 is connected to a cylindrical coupling sleeve 23 throughan end coupler 24, which is also cylindrical.

This end coupler 24 comprises two cylindrical recesses or cavities 25and 26 separated by a bearing 27 comprising two cylindrical surfaces 28and 29 separated by a shoulder 27 a. The surface 28 has an innerdiameter substantially equal to the outer diameter of the head 9 of themulticonductor cable end coupler. The surface 29 has an internaldiameter substantially equal to the external diameter of the threadedportion 1 1 of said end coupler.

The external surface of the end coupler 24 is provided with transversecorrugations 30 in front of recess 25 and its diameter is slightlygreater than the internal diameter of sheath 18. The wall of the endcoupler 24 comprises, on a part of its length, a flat part 31 having athreaded orifice 32 opening inside the end coupler 24 and in which isfitted a plug 33 (FIGS. 6 and 7) and a sealing joint 34 (FIG. 7). r

In the external surface of the end coupler 24, in the vicinity of thebearing 27, there are provided grooves 35 for receiving toric sealingjoints 36 and a threaded housing opening 37 for receiving a screw.Finally, at the end 241 of the end coupler 24, on the side of recess 26there is arranged an electric connector 38 a.

The external diameter of the end coupler 24, at the region of recess 26,is substantially equal to the internal diameter of the coupling sleeve23.

The latter comprises a number of orifices 231 equal to the number ofthreaded housing opening 37.

The coupling of the towing cables 1 and 3 to the end coupler 24 isdescribed with references to FIGS. 7, 8 and 9.

The towing cables 1 and 3 are introduced into the recess 25 of the endcoupler (FIG. 7).

An anchoring element 39 (FIG. 8) of a diameter substantially equal tothe diameter of recess 25 and comprising housing openings in whichcables 1 and 3 are slidable, is introduced in the end coupler and locksthe sleeves 2 and 4 set on the ends of these cables. This anchoringelement is fastened by screwing of a nut 41 on the threaded end 42 ofthe end coupler 24.

A preferred fastening way is that illustrated in FIG. 9. In the externalsurface of the extremity of the end coupler 24, on the side of recess 25and in a diametral plane, are arranged two grooves 43 for the passage ofcables 1 and 3 and two housings 44 for the sleeves 2 and 4.

The advantages of the invention will be better understood from thefollowing description of the assembling of streamer sections and theircoupling.

The sleeve 8 of cable 7, provided with a toric joint 45 (FIG. 7) placedin the groove 10, is introduced into the end coupler 24 up to thebearing 27 and is locked with a nut 46. The conductor bundle inextension of the sleeve is wired on the connector 38 a secured to theextremity 241 of the end coupler 24. A marking pin 47 insures the rightangular positioning of the connector. In order to make easier the cablesetting of the bundle on the connector, port holes 242 (FIGS. 7-9) canbe provided in the external surfaces of the end coupler 24.

The towing cables are fastened through the anchoring element 39 and thenut 41.

Each group of pressure sensors is positioned along the section byintroduction of each sleeve 5 into the housing opening 21 arranged ineach element (FIG. 4). The towing cables and the three conductors ofeach strand 16 are introduced into the corresponding grooves of eachelement 15 and kept in position for example by means of metal or plasticcollars or of thermoretractable sleeves not shown in the figures.

The assembly formed of the towing cables, the conductors, the pressuresensors and the transformer or the impedance adapter-amplifier is thencovered with a sheath of plastic material 18, the ends of which aredrawn on the extremity of the end coupler 24 (FIG. 7), provided withcorrugations and gripped by collars 48.

Conductors 16, connected to the transformer or to the impedanceadapter-preamplifier, are introduced into the end coupler 24 and wiredon the electric connector 38. They pass through the bearing 27, throughone or more channels 49, the sealing of which is achieved by a joint, apacker or by filling with a sealing material (no sealing means is shownin the figures).

The towing cables are introduced into the end coupler and fastened asabove described.

The extremity of the end coupler 24 opposite to the sheath 18 of onesection is then introduced into the coupling sleeve 23. The fasteningand angular positioning of these two elements are achieved by means ofscrews 50 after the orifices 231 have been made to register with thethreaded housing openings 37. The end coupling of the other section isthen introduced in and slided through the sleeve 23 in the same mannerby bringing in coincidence the respective axes of housing openings 37and orifices 231. The electric connectors 38 a and 38 b, guided by theextremities 241 of the end couplers on which they are secured andpositioned by means of the marking pins 47, fit each otherautomatically.

Finally the seismic streamer section is filled with oil via orifice 32.In order to facilitate the filling and emptying, the plug 33 may beprovided with a needle adjusting screw or a non-return valve. The plug33 may also be replaced by a valve directly secured on the end coupler24.

It is noted that the electric connectors are contained in a housingwhich is insulated from the external water by means of sealing joints 36and insulated from the oil filling the cavity by means of sealing joint45.

It is also to be observed that the simplicity of the assembling of thedevice makes easy the replacement or permutation of streamers sections.

It must be understood that the specific arrangement described for thefastening of the towing cables to the groups of pressure sensors is nota limitation of the invention, since it is also possible to make use ofa single sensor per group, to have one or more cables in each sectionand to fasten the sensor to one or more cables in the described manner.

More generally it is clear that, from the foregoing description, oneskilled in the art, can easily ascertain the essential characteristicsof the invention and, without departing from the spirit and scopethereof, can make various changes and modifications of the invention toadapt it to various usages and conditions.

What we claim as this invention is 1. An acoustic wave receiver forunderwater seismic prospecting comprising a plurality of tubularsections filled with liquid and containing coupled pressure transducers,electric conductors interconnecting the transducers, a multiconductorelectric cable having a tight sleeve adjacent each end thereof and anelectrical connector arranged at each end, towing cables and couplingmeans for interconnecting the tubular sections, said coupling meansincluding couplers secured to the ends of the tubular sections, eachcoupler having a wall with an internal protrusion forming a bearing andfirst and second recesses separated by said bearing, means for anchoringthe ends of the towing cables, said anchoring means being secured withinthe coupler at the region of the first recess, means for connecting theelectrical connector in a predetermined angular position substantiallyat the end portion of the coupler containing the second recess andremovable means for fastening the sleeve of the multiconductor cable tosaid bearing, said coupling means also including a coupling member forinterconnection of the couplers, said coupling member having an internalsection substantially equal to the external section of the end of thecoupler containing the second recess and having additional means for theangular positioning and fastening of each coupler, and sealing meansassociated with the external wall of the sleeves of the multiconductorcable and with the end of the coupler contained in the coupling memberfor insulating said second recess of the coupler from the internalliquid of the tubular sections and from the surrounding water.

2. An acoustic wave receiver according to claim 1, wherein thetransducers are externally secured to support members substantiallyfitted to the internal diameter of each tubular section, said supportmembers having grooves arranged in the lateral wall thereof forming apassageway for the electric conductors and the towing cables, and atleast one housing opening being provided in the lateral wall of saidsupport members for receiving anchoring elements secured onto at leastone of the towing cables.

3. An acoustic wave receiver according to claim 1, wherein saidanchoring means for the ends of the towing cables comprise housingopenings arranged in the external wall of each coupler for receivinganchoring elements secured to the ends of the towing cables.

4. An acoustic wave receiver according to claim 1, wherein each couplercomprises at least one channel for the passage of the electricconductors of the tubular section connected with the electricalconnector in the region of the second recess of the coupler.

5. An acoustic wave receiver according to claim 1, wherein the sleevesof the multiconductor electric cable comprise a head portion forabutment against the protrusion of the coupler, said head being providedwith recesses for the sealing means.

l l 1 l

1. An acoustic wave receiver for underwater seismic prospectingcomprising a plurality of tubular sections filled with liquid andcontaining coupled pressure transducers, electric conductorsinterconnecting the transducers, a multiconductor electric cable havinga tight sleeve adjacent each end thereof and an electrical connectorarranged at each end, towing cables and coupling means forinterconnecting the tubular sections, said coupling means includingcouplers secured to the ends of the tubular sections, each couplerhaving a wall with an internal protrusion forming a bearing and firstand second recesses separated by said bearing, means for anchoring theends of the towing cables, said anchoring means being secured within thecoupler at the region of the first recess, means for connecting theelectrical connector in a predetermined angular position substantiallyat the end portion of the coupler containing the second recess andremovable means for fastening the sleeve of the multiconductor cable tosaid bearing, said coupling means also including a coupling member forinterconnection of the couplers, said coupling member having an internalsection substantially equal to the external section of the end of thecoupler containing the second recess and having additional means for theangular positioning and fastening of each coupler, and sealing meansassociated with the external wall of the sleeves of the multiconductorcable and with the end of the coupler contained in the coupling memberfor insulating said second recess of the coupler from the internalliquid of the tubular sections and from the surrounding water.
 2. Anacoustic wave receiver according to claim 1, wherein the transducers areexternally secured to support members substantially fitted to theinternal diameter of each tubular section, said support members havinggrooves arranged in the lateral wall thereof forming a passageway forthe electric conductors and the towing cables, and at least one housingopening being provided in the lateral wall of said support members forreceiving anchoring elements secured onto at least one of the towingcables.
 3. An acoustic wave receiver according to claim 1, wherein saidanchoring means for the ends of the towing cables comprise housingopenings arranged in the external wall of each coupler for receivinganchoring elements secured to the ends of the towing cables.
 4. Anacoustic wave receiver according to claim 1, wherein each couplercomprises at least one channel for the passage of the electricconductors of the tubular section connected with the electricalconnector in the region of the second recess of the coupler.
 5. Anacoustic wave receiver according to claim 1, wherein the sleeves of themulticonductor electric cable comprise a head portion for abutmentagainst the protrusion of the coupler, said head being provided withrecesses for the sealing means.